Cons
- Certain mob types are a pain in the ass (fire-resist golems)
- Must maintain Molten Shell for decent defenses
- Proper flask usage is key for survival
- Searing Touch prohibits some defensive choices late game and may need switched out

Fire Trap is really my main skill, with Fireball to back it up. With the +burning increases with the build + Searing Touch, Fire Trap becomes insane. I practically walk into a room, cast Flammability + Fire Trap, the move on. The clearing power is immense.

Gem setup for Fire Trap is: Fire Trap -> Chance to Ignite -> Elemental Proliferation -> Increased Area of Effect. The concept here is that the burning ground damage is separate from actual ignite damage - if the initial Fire Trap explosion procs an ignite, it'll do damage along with the burning ground. The result pretty much melts everything that doesn't carry natural fire resist or elemental resists, including blue and yellow mobs. Most map bosses are even a joke, except for the fire resist golem types. (I think those are a pain in the ass for a lot of people though)

I use Fireball for cleanup, simple Fireball -> GMP -> Fire Penetration -> Pierce combo. I find Fork and Chain to be woefully subpar for my needs, Pierce does just fine and keeps the damage good and mana constraints small. (My above combo is already 86 mana/cast, which is pretty heavy)

Aside from that, I use the obvious Flammability curse. Enfeeble on the side. I may replace that with Temporal Chains though since a map buddy runs Enfeeble as well. I keep Molten Shell + Increased Duration up constantly for the armor buff. I also run a simple Skele totem, but I only need it about 20% of the time.

Fire Trap CombosFire Trap -> Chance to Ignite -> Elemental Proliferation -> Increased Area of Effect
- This is the combo you want for aoe clearing. In a lot of cases, a single Fire Trap will clear small dungeon rooms by itself. Very powerful when using Searing Touch.

Fire Trap -> Chance to Ignite -> Fire Penetration -> Concentrated Effect
- The fire version of Bear Trap. Great for bosses and tough yellows. Mix in some crit here and you can get some crazy ignites.

Other
A lot of people neglect proper flask usage. You will not succeed with this build without the proper flask setup and knowledge of when and how to use them. While leveling, I used this mana potion until I had enough native regen:

Spoiler

Currently, I run:

Spoiler

Some of these are not optimal, but they have the key properties that I need. The first health flask I pop for the 12s armor buff and increased regen when I anticipate some melee hits. If I take too much damage, the second is used for instant recovery.

I use Quicksilver both offensively and defensively. The ranged LMP/GMP packs do wicked damage with their volleys, but you can easily dodge them with the speed boost and lay a quick Flammability + Fire trap. A good pair of run speed boots is also a necessity here.

Granite flasks don't really need much of an explanation, pop them if you're in melee range of a large group or hard hitter.

I focus mainly on armor gear, but the gear I have right now is actually pretty suboptimal. I barely scrape 2k armor w/o buffs up, I really rely on Molten Shell + Determination right now (and flask usage) to keep my defenses in good shape.

My Hp is a little over 3.5k, which is enough for now, but I would like to optimally be around 4.5 - 5k, which I think is doable with my build in the right gear.

Notes

I would not recommend this build to newer players. It requires a good knowledge of mob types and how they perform, plus proper flask usage in order to survive. Maintaining Molten Shell constantly may be annoying to some. It takes some intelligence, a little twitch skill (sometimes), and consideration for game mechanics (ex., knowing that golem rolling and roa charging is almost impossible to dodge right now due to weird syncing issues with those moves)

That being said, this build can greatly outperform a lot of others out there in terms of damage and clearing speed. (The reason I'm posting this is because I get a lot of people asking me how I do so much damage) It is very much a high-impact playstyle, but if you know what you're doing, survivability is not an issue.

Seems like a good build. I'm using something very similar myself at the moment (link to build, lvl72 atm). I agree with Fireball -> GMP -> Fire Penetration -> Pierce, it is a strong combo. I feel like the fire trap with elemental proliferation might be a great addition.
A few questions, if you dont mind:

1) Are you using Dex on your gear? (Requirement for GMP etc.). Maybe you could just post your current gear, that always provides some more insight.

2) Do you think Crit is that important with this build? How much crit chance/multiplier do you have on Fireball/Trap? I was thinking about going for more spell damage & cast speed instead of crit nodes. Not sure if that would be a mistake.

3) You say Fire Trap is your main skill, yet you prefer using Fireball in the Searing Touch (+2 on the gem). Why is that? Is the scaling on Fire Trap not good enough?

4) How are you running all of these Auras? I have like 1300 Mana and I can't run those even with reduced Mana supports. Are you using Blood Magic support? If so, could you describe your Aura setup in more detail?

5) Are you using a totem (e.g. Skeleton totem) to distract mob packs? Any other form of crowd control, or simply temporal chains?

Is there no benefit to be had from taking the AoE passives? They are very much within reach (Amplify and Blast Radius). There is a +40% radius increase to be had from the seven Templar and Witch nodes, that's a 96% increase in area.

1) Are you using Dex on your gear? (Requirement for GMP etc.). Maybe you could just post your current gear, that always provides some more insight.

Yes, I normally had to keep 1 item around with some dex on it. Gear is posted in the main section now

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2) Do you think Crit is that important with this build? How much crit chance/multiplier do you have on Fireball/Trap? I was thinking about going for more spell damage & cast speed instead of crit nodes. Not sure if that would be a mistake.

Given that i've pretty much had no crit up until the most recent levels, no. Going for spell damage and cast speed should be perfectly fine, you'll just have to make sure you have enough mana regen to handle super fast cast speeds, as Fireball becomes pretty pricey.

I don't like how a lot of the spell damage nodes are budgeted and their general location, so I'm opting for crit instead.

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3) You say Fire Trap is your main skill, yet you prefer using Fireball in the Searing Touch (+2 on the gem). Why is that? Is the scaling on Fire Trap not good enough?

Mostly laziness. I lose a lot of damage off of Fireball if I take it out, and Fire Trap seems to clear packs well enough on its own.

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4) How are you running all of these Auras? I have like 1300 Mana and I can't run those even with reduced Mana supports. Are you using Blood Magic support? If so, could you describe your Aura setup in more detail?

I'm not using any Blood Magic support. Are you using Discipline? The 30% buff passives + increased ES passives will boost the amount you get from it by a lot. My armor helps (almost 200 ES), but I was able to run 4 auras prior to that as well.

My base mana is at 1730, and shoots up to 2453 as soon as I cast Discipline.

If you look at my gear, you'll see an open red gem slot in my helm. I cast Discipline + Clarity, then drag my Reduced Mana to my helm and cast the others. I have roughly over 400 mana left with everything up. I can actually run Determiation + Vitality + Clarity + Discipline + Purity, but I only have a little over 100 mana to use, and it makes it hard to do the 50% reduced regen maps.

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5) Are you using a totem (e.g. Skeleton totem) to distract mob packs? Any other form of crowd control, or simply temporal chains?

I did mention I have skeleton totem. I don't actually have Temporal Chain in use yet, I wanted to try it over Enfeeble though.

The skele totem was an addition at 70+, basically it helps on certain maps if I want to solo. It also helps keep bosses in place to make Fire Trap damage more optimal. While leveling, most of the time it was shoot 'n scoot. I abuse my quicksilver flask and run speed boots help a ton.

You can facetank a lot of white mobs, you tend to get a feel for it as you play. Molten Shell kind of acts as a warning, if big damage is incoming, it'll go off, and that's normally a sign to gtfo. You don't want to be facetanking ANY bosses though, and in general I don't trust my defenses enough to do any sort lengthy tanking. If I'm facetanking something, it's normally to draw them into a Fire Trap.

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Is there no benefit to be had from taking the AoE passives? They are very much within reach (Amplify and Blast Radius). There is a +40% radius increase to be had from the seven Templar and Witch nodes, that's a 96% increase in area.

I had Amplify and Blast Radius for a long time. I'm not sure I could spare the points going for all the smaller ones, but those two passives are decent. I reskilled to put some more points into defensive areas. Fire Trap w/ Increased Area of Effect by itself (and Elemental Proliferation leveled) seems to be enough to clear out rooms for my needs. I could see how the increased area could be useful on larger packs though. I typically just toss an extra trap out if that's the case.

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How do you feel about fire traps build up/cooldown "issue"

if you play pretty much any other build, you walk into a map. hold right click and pick up items.
with trap builds don't you have to hang around waiting for them to refill all the time?

I still have Fireball, which is strong enough on its own to take out packs, it just doesn't do it as fast as a single Fire Trap.

Not starting a zone with any Fire Traps sucks most of the time, but I only need 1 available to start laying down destruction normally.

I don't really spam Fire Trap either, I'll throw one at the larger groups and then clean up with Fireball. The reason I say Fire Trap is my main skill is that it does most of the damage/killing, but I do make use out of my other abilities as well.

I tried throwing in Concentrated Effect as it boosts the Fireball explosion damage by a ton, but it doesn't really work well with Pierce, since a Fireball itself won't explode on a pierce proc. Replacing Pierce with something else (I had Faster Projectiles in) makes things interesting though, as it makes shotgunning with Fireball amazing. I opted out of this though since I dislike having to be in melee range a lot.

Does detonate dead fit into this build at all? how about on a spell totem?

Not really sure on that, Fire Trap wipes out large groups well enough that I imagine Detonate Dead (either by cast or by totem) would be too slow to really have any impact. You could try replacing Fire Trap with it, but your killing speed/power would drop dramatically I would think.

I haven't played with the skill much at all though, so I won't make any absolute judgments on it.